As light oil reserves are gradually being depleted and the costs of development (e.g., lifting, mining, and extraction) of heavy oil resources have increased, a need has arisen to develop novel upgrading technologies to convert heavy oils and bitumens into lighter products. With the advent of heavier crude feedstock, refiners are forced to use more catalysts than before to upgrade the heavy oil and remove contaminants/sulfur from these feedstocks. These catalytic processes generate huge quantities of spent catalyst. With the increasing demand and market price for metal values and environmental awareness thereof, catalysts can serve as a secondary source for metal recovery.
In order to recycle/recover catalytic metals and provide a renewable source for the metals, efforts have been made to extract metals from spent catalysts generated from heavy oil upgrade processes, whether in supported or bulk catalyst form. Before catalytic metals can be extracted/recovered from spent catalysts, residual heavy oil from hydroprocessing operations has first to be separated from the spent catalysts. Effluent streams from heavy oil upgrade system typically contain unconverted heavy oil materials, heavier hydrocracked liquid products, slurry catalyst ranging from 3 to 50 wt. %, small amounts of coke, asphaltenes, etc. Conventional filtration processes may not be suitable to separate/recover slurry catalyst from high molecular weight hydrocarbon materials in the effluent streams as the unsupported fine catalyst may cause plugging or fouling of filters.
Membrane technology has long been used in removal of contaminants in environmental clean-up, wastewater treatment and water purification, particularly with the use of microfiltration, ultrafiltration, nanofiltration and reverse osmosis. Nanofiltration has more recently been used to purify/remove impurities such as vanadium (in ppm amounts) from low boiling hydrocarbon mixtures boiling such as kerosene.
Heavy oil exposed to hydrocracking conditions is particularly difficult to extract/remove/separate from slurry catalyst. Conventional solvent extraction and roasting methods in the prior art do not work particularly well with slurry catalyst, leaving heavy oil behind with the catalyst particle, thus creating problems in the downstream metal recovery process (recovering valuable metals from spent catalyst). Some chemicals in the residual entrained oil in catalyst particles cause foaming issues during the metals recovery process and negatively impact any attempts at metals recovery using chemical extraction, pressure leaching, metal digestion/solubilization, crystallization, and or precipitation methodologies.
The present invention relates to novel applications of membrane technology in separating and/or extracting residual heavy oil from spent catalyst particles generated from heavy oil upgrade operations, and subsequently removing residual heavy oil from catalyst particulates to less than 0.5 wt. % in one embodiment.